June 19, 2014:
The U.S. Air Force recently announced that the long rumored RQ-180 UAV did indeed exist and was still in development. The RQ-180 is a large (over 12 tons) and stealthy UAV designed to survive in heavily defended air space. The earlier RQ-170, which first saw service over Afghanistan and South Korea in 2010 is a similar, but smaller and earlier design. The U.S. Air Force had already admitted that the RQ-170 was a high altitude reconnaissance UAV developed in secret by Lockheed-Martin during the previous decade. It has a 12 meter (40 foot) wingspan. The RQ-170 is believed to be a replacement for some of the U-2s and a supplemental aircraft for the larger Global Hawk (which has a 42 meter wingspan). RQ-170s were also suspected as being the basis for a larger and stealthier UAV and this is now revealed to be the RQ-180.
Both the RQ-170 and RQ-180 are jet propelled UAVs employing a flying wing design, similar to the X-45s and X-47s built as development aircraft for the U.S. Air Force and Navy. These UCAVs (Unmanned Combat Aerial Vehicles) were built to carry weapons while the similar looking reconnaissance UAVs just carry sensors internally. The RQ-170 and RQ-180 are purely reconnaissance aircraft. The RQ-170 weighs about six tons while the larger RQ-180 weighs at least twice as much. Endurance of the RQ-170 is about six hours while the RQ-180 can stay up three to four times longer. The RQ-180 also carries more capable sensors, apparently some of the ones used in the 14 ton RQ-4 Global Hawk. There are about twenty RQ-170s in service while only about half a dozen RQ-180s have been built so far.